54's are kinda special as that is the year Marlin switched to M.G. rifleing.
If its a Ballard rifled model add a little to its worth .
If its a Mountie , straight stock add a little more to its worth.
If its a Mountie with Ballard rifleing and in good of shape as you say you need to buy it ASAP as it would be one of 54 built that year .
I have 2, 54 Mounties with M.G. rifleing in very good condition , I value them at about $675.00-$700.00 apiece as they are 2 of 1182 built in 1954.
All 54's should demand a little higher price because they are eather first year or last year models .
Congrats on a good find .